The authors describe a new radionuclide method for assessing the functional integrity of slow intrathecal infusion devices. Approximately 11 mCi (400 MBq) of Tc-99m DTPA is injected into the pump chamber. Early and delayed imaging of the pump, tubing, and spinal cerebrospinal fluid space is performed on a digital large-field-of-view gamma camera. The digitally displayed images are then reviewed by adjustment of the grey scale window. Four patients have had eight studies and in each case the result has been confirmed by surgical exploration or by clinical response to change in therapy.